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|United States Patent
,   et al.
August 19, 1997
Method and apparatus for improving data regeneration in asynchronous
A method and apparatus for improving data regeneration in an asynchronous
communication network is described where data is received on a two wire
connection bus at a node in a communication network and is immediately
retransmitted to another node therein. Incoming serial data is sampled at
the time center of the serial data bit and is then immediately
retransmitted based on the sampled data. The delay associated with
buffering one full byte of data is reduced by a factor of 20 since the
improved data regeneration technique of the present invention immediately
retransmits the regenerated data one-half bit after it is received.
Therefore, the network throughput is increased by a factor of 2000% and
the network transmission media length is increased by a factor
corresponding to the number of network nodes.
Vielhaber; Timothy J. (Avon Lake, OH);
Sudnick; Tina M. (Grafton, OH)
Grinnell Corporation (Exeter, NH)
April 28, 1995|
|Current U.S. Class:
||375/213; 375/214 |
|Field of Search:
U.S. Patent Documents
|4334303||Jun., 1982||Bertin et al.||370/13.
|4611324||Sep., 1986||Giacometti et al.||370/97.
|4710976||Dec., 1987||Wakabayashi et al.||370/13.
|4930118||May., 1990||Sugihara et al.||370/13.
|4937812||Jun., 1990||Itoh et al.||370/13.
|5231629||Jul., 1993||Kotzin et al.||375/214.
|Foreign Patent Documents|
|2 216 366||Oct., 1989||GB.
Murdock, G., et al., "Build a Direction-Sensing Bidirectional Repeater",
Electronic Design, (vol. 37, No. 10), May 11, 1989, as reprinted in
National Semiconductor Application Note 702, AN-702, pp. 1-368-1-372.
Primary Examiner: Tse; Young T.
Attorney, Agent or Firm: Keck, Mahin & Cate
1. A method for regenerating data in asynchronous network communication,
(a) receiving data from a first data transceiver of a first node of a
(b) sampling said data from said first data transceiver at the time center
of a first data bit;
(c) verifying whether said data has been received by said first data
(d) regenerating said data for transmission to a second node in the
(e) steering said regenerated data to a second data transceiver in response
to receiving of said data at said first node; and
(f) transmitting said regenerated data from said second data transceiver to
said second node in the communication network a fraction of a bit time
after it is received at said first node.
2. A method for regenerating data in asynchronous network communication as
set forth in claim 1, wherein said data is transmitted along a two way
3. A method for regenerating data in asynchronous network communication as
set forth in claim 1, wherein said communication network is directed to a
fire control system.
4. A communication node for regenerating and retransmitting data in a
communication network, which comprises:
(a) a first data transceiver for receiving data which includes serial data
bits, at a first node of a two way communication bus of said communication
(b) a valid data detector for verifying said data and generating a signal
in response to receipt of said data by said first data transceiver;
(c) a dual universal asynchronous receiver/transmitter for receiving said
data from said first data transceiver and for sampling said data at the
time center of a first data bit and for regenerating data;
(d) a data/control steering logic circuit for steering said regenerated
data from said dual universal asynchronous receiver/transmitter upon
receipt of said signal from said valid data detector; and
(e) a second data transceiver for retransmitting said regenerated data into
the communication network from said data/control steering logic circuit
one half bit after receiving said data at said first data transceiver.
5. A communication node as set forth in claim 4, wherein said communication
network is directed to a fire control system in a building.
6. A communication node as set forth in claim 4, wherein said data is
regenerated and retransmitted with a one half bit delay after being
received at said communication node.
7. A communication node as set forth in claim 4, wherein said communication
node is for use in a fire control system.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This present invention relates to an improved method and apparatus for data
regeneration in asynchronous network communication.
2. Description of Prior Art
Communication networks which transmit data over wire or fiber are limited
in the distance in which the data may be transmitted and successfully
recovered at the receiving end. The physical properties of the
transmission media as well as the properties of the data transmitter and
data receiver determine the maximum communication distance, 1, between
transmitter and receiver. In networks that do not implement any type of
data repeater or regeneration, the length, 1, is the maximum length for
the entire network.
Prior art data repeaters have been utilized in long communication lines to
increase the distance between the transmitter and receiver. The repeaters
typically work by amplifying the signal. Direction sensing bi-directional
repeaters are known in the art and are described, for example, in an
article by Gary Murdock and John Goldie entitled Build a Direction-Sensing
Bidirectional repeater, Vol. 37, No. 10, Electronic Design, May 11, 1989,
reprinted in National Semiconductor AN-702. These prior art repeaters,
however, only amplify the signal and do not regenerate the data as new,
clean data. Therefore, if there is any distortion or noise in the data, it
is not corrected by the repeater.
To solve the problem of distorted data, various methods of asynchronous
network communication provide for data regeneration at each node of the
communication network which typically involves the buffering of a portion
of the data in the receiving node before regenerating and retransmitting
the data to the next node of the network. The current methods of data
buffering require that the entire message (i.e., one to m bytes of data)
or at a minimum, one byte of date (8 data bits plus a start and stop bit)
be buffered by the receiving node before the data is regenerated and
retransmitted to the next node in the communication network. By using data
regeneration at each of the network nodes, n, the overall network
transmission media length can be increased such that an overall length of
n.times.1 can be achieved.
These prior art repeaters and data regenerators fail to accomplish the
objects set out below which include significantly reducing the data
buffering to one half bit of data, and therefore significantly increasing
the network throughput, while at the same time providing the n.times.1
overall network transmission media length.
SUMMARY OF THE INVENTION
The general object of the present invention is to improve the method of
data regeneration in asynchronous network communication by reducing data
buffering to a minimum. The reduction of the data buffering requirement to
one half bit of data significantly improves and increases the asynchronous
network communication throughput over previous data regeneration
techniques found in the prior art. Data is sampled during the middle of
the data bit, then it is regenerated and retransmitted to the next
communication node. In prior art data regeneration techniques, a byte of
data is buffered before the data is regenerated and retransmitted to the
next node of the communication network.
The improved data regeneration technique yields an effective 2000%
improvement in the data regeneration time which translates into a 2000%
improvement in network throughput.
It is another object of the invention to steer data (to be retransmitted)
among the two data ports that are associated with each communication node.
By steering the data, valid data from either port can be regenerated and
directed out the other port automatically. Therefore, there is no need for
a dedicated transmit port and a dedicated receive port.
It is a further object of the invention to provide the maximum wiring
distance between nodes and the maximum overall wiring distance for the
communication network. By implementing this data regeneration technique,
the maximum wiring distance, 1, of many current communication networks can
be supported between each node, thereby improving the wiring distance
capacity of an n node network from 1, to n*l.
The above, as well as additional objects, features and advantages of the
invention will become apparent in the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating the asynchronous communication data
FIGS. 2A and 2B are circuit diagrams of the preferred embodiment of the
FIG. 3 is a state diagram of the programmable array logic employed by the
preferred embodiment of the invention.
FIG. 4 is a timing diagram of a prior art data regeneration technique.
FIG. 5 is a timing diagram of the improved data regeneration technique of
The preferred embodiment of the invention is directed to a fire control
system for use in a building, structure or the like. The various nodes of
the fire control system each include processing hardware in combination
with sensors and control actuators. The nodes are connected throughout the
building by a two-wire connection bus which permits two way communication
FIG. 1 shows a block diagram of the asynchronous communication data
regeneration technique utilized in the fire control system. A two-wire
connection bus 1,2 associated with port 1 and a two-wire connection bus
3,4 associated with port 2 connects all the nodes of the control system
throughout the building providing two way communication. If a serial data
stream arrives at port 1, a port 1 data transceiver 5 receives the serial
data while valid data detector 6 simultaneously determines whether the
serial data is valid. The valid data detector 6 sends a signal to the
data/control steering logic 7 if the data is valid so that the
data/control steering logic 7 will automatically steer the regenerated
data out port 2.
The port 1 data transceiver 5 transmits the data to one port of a dual
universal asynchronous receiver/transmitter (DUART) 8 which transmits the
data to the data/control steering logic 7. The DUART 8 is operated in an
automatic echo mode which receives the digital data and regenerates and
retransmits the data with a one half bit delay. The data/control steering
logic 7 steers the data to the port 2 data transceiver 9 based on the
signal from the valid data detector 6. The data/control steering logic 7
controls the steering Of the data from the receiver to the transmitter for
transmission to the next node. It should be noted that the two way
communication flow of the bus allows the data flow to be reversed with the
input going into the port 2 data transceiver 9 and the output being
directed out the port 1 data transceiver 5.
FIG. 2 shows a detailed circuit diagram of the preferred embodiment of the
asynchronous communication data regeneration circuit of the fire control
system. The port 1 and 2 data transceivers 5 and 9, respectively, are
identified in block (a) of FIG. 2. The valid data detector 6 is identified
as block (b) of FIG. 2 and determines whether the input data is valid. A
PAL 10 in FIG. 2 programmed as a repeater state machine logic array
comprises the data/control steering logic 7 which steers the valid data
out the appropriate port in response to signals from the valid data
detector 6. The shift register 16 and AND-gates associated with each
channel form a digital filter and signifies valid data.
The repeater state machine PAL 10 steers the regenerated data out the
appropriate output port while reducing the data buffering requirement to
one half bit of data. The pin-out of the repeater state machine PAL 10
corresponds to the following:
PIN 1 CLOCK ; 16x CLOCK FROM DUART
PIN 4 LV1 COMB ; VALID 0 ON LEFT RS485 CHANNEL
PIN 5 LV0 COMB ; VALID 1 ON LEFT RS485 CHANNEL
PIN 6 RV1 COMB ; VALID 0 ON RIGHT RS485 CHANNEL
PIN 7 RV0 COMB ; VALID 1 ON RIGHT RS485 CHANNEL
PIN 8 BL COMB ; LEFT CHANNEL VALID DATA
PIN 9 BR COMB ; RIGHT CHANNEL VALID DATA
RST COMB ; CHIP RESET
EN COMB ; REPEATER ENABLED
GND ; GROUND
RTSL COMB ; LEFT CHANNEL RTS
ST1 REG ; STATE BIT 1
ST0 REG ; STATE BIT 0
RTSR COMB ; RIGHT CHANNEL RTS
VCC ; POWER.
Note, not all the pins listed above are employed in the circuit
implementation of FIG. 2.
The DUART 8 in FIG. 2 receives the digital data and regenerates and
retransmits the data with the one half bit delay. The DUART 8 samples the
incoming serial data at the time center of the serial data bit. With this
sample of the data, the DUART 8 determines whether the data bit is a 0 or
a 1 and then immediately begins retransmitting the data out its transmit
line, based on the sample of the data. The data is output through the
appropriate port data transceiver by multiplexer 15 based on whether
regenerated data is being sent out to the communication network or whether
the data originated from the node. The data is not sampled until the
middle of the data bit to minimize the possibility of incorrectly
interpreting the data and then is immediately retransmitted. The half bit
delay is required because the DUART cannot correctly identify whether the
received bit is a 1 or 0 until half of the bit has been received. A
microprocessor communicates with the DUART 8 via parallel data
transmission and the data is available for transfer to the microprocessor
over its parallel data bus after the start and stop bits are stripped off
the serial data byte.
FIG.3 is a state diagram of the logic implemented by the repeater state
machine PAL 10 (FIG. 2) of the data/control steering logic 7 in FIG. 1.
The state diagram of FIG. 3 provides a graphical representation of the
logic that is employed to steer a valid data stream. Each circle 12 in the
state diagram of FIG. 3 represents a possible internal state of the
repeater state machine PAL 10. The information that is associated with
each possible internal state of the repeater state machine PAL 10 is
defined by the following Boolean Equation Segments:
IDLE--Both channels of repeater in listen mode;
VALID.sub.-- L--Valid data on left channel; and
VALID.sub.-- R--Valid data on right channel.
The arrows 13 connecting each state indicate a permissible transition
between the corresponding states and are represented by the state
transition numbers 14 in parenthesis. The permissible state transitions
are the input conditions under which the transition between states will
occur and are defined by the following state transition equations:
IDLE := COND1 -> VALID.sub.-- L
+ COND3 -> VALID.sub.-- R
VALID.sub.-- L := COND2 -> VALID .sub.-- L
VALID.sub.-- R := COND4 -> VALID.sub.-- R
Each state transition number 14 is defined by the following state condition
where COND1 corresponds to "(1)" in FIG. 3, COND2 corresponds to "(2)",
etc. The state output equations and state assignment equations which
correspond to the state diagram in FIG. 3 are as follows:
State Output Equations
State Assignment Equations
FIG. 4 is a timing diagram of a prior art data regeneration technique.
Referring to FIG. 4, the data byte (consisting here of a start bit, 8 data
bits and a stop bit) is transmitted from node 0 at time=0. The full data
byte can be assumed to be received at node 1 at the same time node 0
completes transmission of the data (i.e., there are no delays associated
with the transmission media). In the prior art data regeneration
technique, data can begin to be retransmitted only after the full byte has
been received, at time=10. The data is then fully received at node 2 at
time t=20. Therefore, the total delay between the first transmitted data
bit and the first received data bit at node n is given as:
FIG. 5 is a timing diagram of the improved data regeneration technique of
the invention. In the improved data regeneration technique, the data can
begin to be transmitted one half bit time after it is received at node 1,
at time=0.5. The data is then fully received at the second node at
time=10.5. The total delay between the first transmitted data bit and the
first received data bit at node n is given as:
The delay in a data bit being transmitted by node 0 and being received at
node n is given by (n-1) *10 for the prior art data regeneration technique
and given by (n-1) *0.5 for the improved data regeneration technique.
Comparing the delays associated with the prior art and the improved
technique illustrates that the improved technique is 10/0.5=20 times
(2000%) better than the prior art method.
The method and apparatus for improving data regeneration in asynchronous
network communication described above have several advantages over the
prior art which should be apparent to those skilled in the art from the
specification. The preferred embodiment of the invention may be changed
without departing from the scope of the invention and should be construed
as illustrative and not as limiting the invention as described herein.